1. Field of the Invention
This invention relates to an accessing method, and an information processing method including recording/reproducing/erasing of information and an information processing device utilizing the same.
More particularly, it pertains to an accessing method which has enabled high speed access of a probe electrode to a plurality of recording regions or reproducing regions in recording by use of a scanning tunnelling microscope (STM), and to an information processing method and an information processing device utilizing the same.
2. Related Background Art
In recent years, uses of memory materials form the nucleus of electronics industries such as computers and related instruments thereof, video discs, digital audio discs, etc., and developments of their materials have been actively progressed. Performances demanded for memory materials, which may differ depending on uses, may be generally as follows:
(1) high density and large recording capacity;
(2) quick response speed in recording and reproducing;
(3) small consumption of power;
(4) high productivity and low cost, etc.
In the past, semiconductor memories or magnetic memories employing magnetic materials or semiconductors as the base materials have been predominantly used, but in recent years, with the progress of laser technique, recording medium of low cost and high density according to optical memory by use of an organic thin film such as organic dye, photopolymer is launched into the arena.
On the other hand, recently, a scanning tunnelling microscope (hereinafter abbreviated as STM) which observes directly the electron structure of the surface atom of a conductor has been developed [G. Binnig et al., Phys. Rev. Lett., 49, 57 (1982)], whereby it has become possible to measure real spatial images of high resolution irrespectively of whether they are single crystalline or amorphous. Besides, it has the advantage that observation can be done at low power without damaging the medium with current, and further it can be actuated in air and therefore used for various materials. For such reasons, a wide scope of applications has been expected.
STM utilizes the phenomenon that tunnel current flows when a probe of a metal (probe electrode) and an electroconductive substance are approached to a distance of about 1 nm with application of a voltage therebetween. This current is very sensitive to the change in distance between the probe and the substance, and by scanning of the probe so as to maintain a constant tunnel current, the surface structure of the real space can be drawn and at the same time various information concerning the whole electron cloud of the surface electrons can be read. In this case, resolution in the interplanar direction is about 0.1 nm.
Accordingly, by applying the principle of STM, it is possible to perform high density recording and reproducing sufficiently at atomic order (subnanometer). As the recording and reproducing method in this case, there have been proposed the method in which recording is performed by changing the surface state of an appropriate recording layer by use of a high energy electromagnetic wave such as particulate rays (electron beam, ion beam) or X-ray, etc. and an energy ray such as visible, UV-ray, etc. and reproducing is effected by STM, or the method in which a material having the memory effect to the switching characteristics of voltage current such as a thin film layer of a .pi.-electron type organic compound or a chalcogenide is used as the recording layer, and recording and reproducing are performed by use of STM, etc. (Japanese Laid-open Patent Application Nos. 63-161552, 63-161553). For example, according to this method, if the bit size of recording is made 10 nm, recording and reproducing with a capacity as large as 10.sup.12 bit/cm.sup.2 is possible.
In realizing the prior art example as mentioned above, a precision of a nanometer or less is required for relative registration between the probe electrode and the recording medium, and also high rigidness in the apparatus (a structure having a high resonance frequency) and high speed characteristics during recording and reproducing are demanded to be possessed in combination.
Under the present situation, a driving device which can satisfy these performances is a piezoelectric device, but since the practical limit of stroke depending on the dielectric strength is about 10 .mu.m, if a piezoelectric device alone is used as the driving mechanism for relative registration of the probe electrode and the recording medium, the recording region becomes smaller as 10 .mu.m square, whereby the recording capacity becomes smaller as 10.sup.6 bit/cm.sup.2. Therefore, for enlargement of capacity, it is required to combine coarse adjustment with the driving mechanism, and when leading into the fine adjustment region by a piezoelectric device from the coarse adjustment region, it has been necessary to provide a positional standard pattern for fine adjustment having a structure than the coarse adjustment precision.
However, according to such method, since the positional standard pattern for fine adjustment is dimensionally scanned and registration of the fine adjustment region is effected from its dimensional image, there is involved the drawback that a long time is required for dimensional scanning of the probe electrode and dimensional image data processing during access of the probe electrode to the recording region.